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TMJ

TMJ. TMJ?. TEMPOROMANDIBULAR JOINT. The only joint in the head?. No. Type of the joint?. Synovial. Bone Muscle Ligaments Innervation Function. LEARNING OBJECTIVE. Describe the anatomical structures of the joint Explain the articulating surfaces of the bones

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TMJ

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  1. TMJ

  2. TMJ?

  3. TEMPOROMANDIBULAR JOINT

  4. The only joint in the head?

  5. No

  6. Type of the joint?

  7. Synovial

  8. Bone • Muscle • Ligaments • Innervation • Function

  9. LEARNING OBJECTIVE • Describe the anatomical structures of the joint • Explain the articulating surfaces of the bones • Describe the embryology of the joint • Identify: capsule, synovial membrane, ligament and articulating disc • Describe the muscles and the movements that take place in the joint • Describe the nerve and blood supply to the joint • Explain how dislocation of the joint can occur

  10. TMJ • Joint/ articulation? • Connection between two separate parts of skeleton • Mandible and the two temporal bones • Craniomandibular joint • Bilateral articulation • the only visible movable joint in the head

  11. Exercise • Palpate the TMJ

  12. Three articulating parts: • Articular eminence (or tubercle) • Articular fossae • Mandibular condyle • Enclosed by fibrous connective tissue capsule

  13. Mandibular condyle • Surface covered by thickened layer of fibrous connective tissue

  14. Articular fossa and articular eminence • Articular fossa – non functioning portion • Articular eminence • functioning portion • Just anterior to the articular fossa • Lined by thicker layer of fibrous tissue

  15. Articular disc • Tough oval pad of dense ficrous connective tissue • Surface – smooth • Thinner in the centre than around the edges • Concave anteriorly to fit under the articular eminence • Convex posteriorly to conform to the shape of articular fossa • Flattened disc  problems

  16. Articular disc • Function: • Partitioning the complex condylar movement into upper and lower functional components • Lubricating with synovial fluid • Stabilising condyle • Cushioning the loading • Reducing physical wear and strains • Helping regulate movements of the condyle

  17. http://www.youtube.com/watch?v=4CVbHsnB3Rk

  18. How does TMJ differ from other synovial joints? • TMJ develops between 8 – 14 weeks compared to 5-8 weeks for other synovial joints • TMJ – initially widely separated temporal and condylar blastema that grow towards each other • Limb joint develops to adulthood by cavity fromation within single blastema • Fibrous cartilagerather than hyaline cartilage

  19. Embryology • 10 – 12 weeks pc • Ossificationof the temporalcomponentsbeginsindependentlyof the events in the mandible • the condylarcartilage is present at the most superior aspect of the ramus. • the embryonicconnective tissue (mesenchyme) betweenthe growingcondyleandtemporalbonecondensesto form the articulardisc • Inferiorcompartment form first (10 weeks) , upper (11.5) • cavitationforms the lower joint compartmentandthenthe uppercompartment

  20. 14 weeks • Joint development completed

  21. Development • Infants: • Articular fossa, articular eminence and condyle – flat • About the same level as occlusal plane • Why? • During development • Articular fossa deepens • Articular eminence - > prominent – when? • Condyle becomes rounded

  22. Growth • Structure grow laterally – widening of the neurocranium • Mature disc – changes shape, more compact, less cellular, more collagen • Condyle contains cartilage • After eruption of permanent dentition, articular tubercle becomes prominent • Accelerates until 12th year of life

  23. Fibrous capsule • Sheet/sac/tube of tissue • Encloses the joint • Fairly thin • Lateral – temporomandibular ligament • Attachment – upper – circumference of articular fossa • Lower – neck of the condyle

  24. Two layers: • Inner layer (synovial membrane) • Lines fibrous capsule • Covers the bone • Secretes synovia – lubricates and nourishes • Outer layer • Thicker layer of fibrous tissue • Accessory ligaments

  25. Ligaments • Capsular ligament – restricts posterior movement of condyle • Temporomandibular ligament • Attachment – upper – zygoma arch, lower – side and back of condyle neck • keeps condyle close to the fossa • Helps prevent lateral and posterior displacement • Stylomandibular ligament • Posterior to the joint • Attached at the _____ and _____ • Sphenomandibular ligament • Medial to the joint • Limit maximum opening • Attached to ______ and _______

  26. Articular disc • Dense fibrous connective tissue • Between mandibular condyle and articular fossa/eminence • Thinner – center • Anteriorly and laterally • Act as a buffer

  27. Muscles • Muscles of mastication • Masseter • Temporalis • Medial pterygoid • Lateral pterygoid

  28. Masseter • Most superficial, powerful • Quadrilateral • Origin: Zygomatic arch – inferior and medial surface and temporal process of zygomatic bone • Insertion: lateral surface of the ramus • Function: closes jaw, crushing

  29. Temporalis muscle • Fan shaped, large but flat muscle • Origin: entire temporalis fossa(part of frontal and parietal bone, squamous part of temporal and greater wing of sphenoid) • Directed downward (anterior), downward, anteriorly (posterior part) – passing medial to zygomatic arch • Insertion: coronoid process, anterior border of ramus and temporal crest • Action: elevator, retractor

  30. Medial pterygoid • Medial to ramus • Origin: medial surface of lateral pterygoid plate and pterygoid fossa, pyramidal process of palatine bone • Pass downward, laterally towards the angle of mandible • Insertion: medial surface of mandible in triangular region • Action: elevator

  31. Lateral pterygoid • Horizontal fibres • Short, thick • Located in the infratemporal fossa • Prime mover of mandible except closing • Origin: 2 heads – upper head – infratemporal surface on great wing of sphenoid • Lower head – lateral side of pterygoid plate on sphenoid bone • Insertion: upper head – neck of condyle and anteroposterior surface of capsular ligament, into disc • Lower head – roughened pterygoid fovea on anterior surface of neck of condyle

  32. Action: opening the jaw • Pulling articular disc and condyle forward down onto articular eminence

  33. Innervation • Proprioceptive neurons in capsule and disc • Trigeminal nerve (cranial nerve V) – auriculotemporal branch of ______ • Branches of mandibular division of the TN (auriculotemporal, deep temporal and masseteric) supply the joint

  34. Blood supply • branches of external carotid artery • Ascending pharyngeal and superficial temporal branches • Anterior tympanic • Massteric • Middle meningeal branch of maxillary artery • -

  35. Problem

  36. RECAP

  37. Name the bony components of TMJ? • Muscles that close the jaw • Nerve innervate the joint

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